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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
        * {
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            margin: 0;
        }

        li {
            list-style: none;
        }

        body {
            background: #f6f9fc;
            font-family: arial;
        }

        .calendar {
            width: 210px;
            margin: 0 auto;
            padding: 10px 10px 20px 20px;
            background: #eae9e9;
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        .calendar ul {
            width: 210px;
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            padding-bottom: 10px;
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        .calendar li {
            float: left;
            width: 58px;
            height: 54px;
            margin: 10px 10px 0 0;
            border: 1px solid #fff;
            background: #424242;
            color: #fff;
            text-align: center;
            cursor: pointer;
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        .calendar li h2 {
            font-size: 20px;
            padding-top: 5px;
        }

        .calendar li p {
            font-size: 14px;
        }

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            border: 1px solid #424242;
            background: #fff;
            color: #e84a7e;
        }

        .calendar .active p {
            font-weight: bold;
        }

        .calendar .text {
            width: 178px;
            padding: 0 10px 10px;
            border: 1px solid #fff;
            padding-top: 10px;
            background: #f1f1f1;
            color: #555;
        }

        .calendar .text h2 {
            font-size: 14px;
            margin-bottom: 10px;
        }

        .calendar .text p {
            font-size: 12px;
            line-height: 18px;
        }
    </style>
</head>

<body>
    <div id="tab" class="calendar">

        <ul id="ul">
            <li class="active">
                <h2>1</h2>
                <p>JAN</p>
            </li>
            <li>
                <h2>2</h2>
                <p>FER</p>
            </li>
            <li>
                <h2>3</h2>
                <p>MAR</p>
            </li>
            <li>
                <h2>4</h2>
                <p>APR</p>
            </li>
            <li>
                <h2>5</h2>
                <p>MAY</p>
            </li>
            <li>
                <h2>6</h2>
                <p>JUN</p>
            </li>
            <li>
                <h2>7</h2>
                <p>JUL</p>
            </li>
            <li>
                <h2>8</h2>
                <p>AUG</p>
            </li>
            <li>
                <h2>9</h2>
                <p>SEP</p>
            </li>
            <li>
                <h2>10</h2>
                <p>OCT</p>
            </li>
            <li>
                <h2>11</h2>
                <p>NOV</p>
            </li>
            <li>
                <h2>12</h2>
                <p>DEC</p>
            </li>
        </ul>

        <div class="text" id="txt">
            <h2 id="h">1月活动</h2>
            <p>快过年了，大家可以商量着去哪玩吧～</p>
        </div>

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</body>

</html>